Effects of landscape, conspecifics and heterospecifics on habitat selection by breeding farmland birds: the case of the Calandra Lark (Melanocorypha calandra) and Corn Bunting (Emberiza calandra)

摘要

The aim of habitat selection studies is to understand the effect of the different factors affecting the spatial distribution of individuals. Within this framework, the aim of this study was to evaluate the relative contributions of landscape features and conspecific and heterospecific interactions to habitat selection by two sympatric species, the Calandra Lark Melanocorypha calandra and the Corn Bunting Emberiza calandra, during the breeding season. During the 2008 breeding season, the population of both species was censused in three Central Spanish locations by means of transects (N = 58). A model-averaging approach was used to determine the weight and effect of landscape and interaction variables in each species' habitat selection using abundance as the dependent variable. Deviance partitioning was used to determine the unique and shared contributions of these two sets of variables to the variation explained by the models. Calandra Lark was positively associated with mean field size, which reflects its preference for relatively simplified landscapes with a low density of field margins and, consequently, small land-use diversity. Corn Bunting selected areas with high land-use diversity, namely, a highly heterogeneous landscape with a high density of field margins. Attraction between conspecifics was found in both cases. Calandra Lark seems to negatively respond to the proximity of Corn Buntings, which indicates a partitioning of space and food resources. However, Corn Bunting responded positively to the proximity of Calandra Larks, which reflects a higher tolerance of Corn Buntings to the presence of other species nearby. Deviance partitioning showed that interactions were more important for Calandra Lark, while Corn Bunting was equally affected by both components. An appropriate management should combine the requirements of both species to achieve effective conservation at the bird assemblage level.